Method for producing gas turbines and gas turbine assembly

ABSTRACT

The invention relates to a production method and to an assembly for a gas turbine system having a low output, which can be used as a shaft output gas turbine, a hot gas generator or as an air supplier. The aim of the invention is to provide a method with which small gas turbines can be produced with the most cost-effective components. The novel method is characterized in that at least one exhaust gas turboblower ( 1 ) of internal combustion engines, and air heaters ( 11, 12 ) that are manufactured or adapted with regard to the output parameters of the exhaust gas turboblower are joined to additional subassemblies, which are also adapted to said exhaust gas turboblower, in order to form a gas turbine. The outlet of the compressor ( 5 ) of the exhaust gas turboblower ( 1 ) is connected to the gas producer i.e. to the combustion chamber ( 12 ).

PRIOR ART

Gas turbine assemblies, called gas turbines for short, are of greatimportance these days in drive technology. They are distinguished by alow specific weight, uncomplicated handling as well as by vibration-pooror vibration-free operation based on principle. On the other hand, thereis a high manufacturing cost and consequently a high purchase price.Nevertheless, gas turbines have prevailed as a drive unit for mechanicalpowers of down to about 220 kW, if the gas-turbine specific advantagesare to be fully used (e.g. aeronautical drives). Below thisaforementioned power limit, gas turbines have little or no significance,primarily due to the high purchase price which is up to ten timesgreater in comparison to an equally powerful reciprocating engine.Reciprocating engines are still used in this circumstance today,although the use of a gas turbine would be technically more advantageousand comfortable (e.g. vibration-free). Compact gas turbines are designedand manufactured nowadays in such a way that a large number of theindividual components must be developed and manufactured exclusively forthis one purpose. Among other things, this also includes the rotors(turbine wheels, impeller compressors) and their blades, shafts,distributors and bearings which are especially expensive and demandingin the material selection. Replacing assembly groups and individualcomponents is only possible to a limited degree or not at all when theturbine output and/or the type of turbine is to be changed. Assemblygroups cannot simply be replaced, so that only a single type of gasturbine can be produced with the developed parts.

A method for effectively manufacturing small gas turbines is proposed inDE 3 701 519 A1. The invention relates to the manufacture of standardcomponents from which modules are prefabricated. Gas turbinescorresponding to the specific application are produced by combiningthese modules and connecting them by lines. Although high unitproduction numbers and consequently reductions in cost are obtained withthis solution, a special production for turbine wheels, bearings, etc.is required. However, the technical expenditure and costs are stillconsiderably higher than with internal combustion engines. Thecombination of modules always means a compromise with respect to theagreement of the parameters which result in power losses. Moreover, dueto the required long connection lines, additional expenditures and greatpower losses (flow resistance, heat losses) result which have anespecially negative affect with the low performance. The advantages ofthe spatially separate assembly groups are only desirable in a fewapplications. Predominantly, a compact drive unit is required.

OBJECT OF THE INVENTION

The object of the invention is to create a method with which small gasturbines can be produced with cost-effective components. A furtherobject is to develop assemblies in order to be able to create variouscompact gas turbines with these components.

According to the invention, this object is solved according to thefeatures of claim 1.

Very cost-effective gas turbine assembly groups and components areprovided for small gas turbines with this suprisingly simple solution.

Exhaust-gas driven turbines on reciprocating engines have been known formany years and in various sizes. They convert the energy of theexhaust-gas flow into compressor power for the engine charge. Their usefor other applications or generally as gas turbines have been overlookedto date by the trade. Furthermore, to use existing turbochargers forproducing gas turbines, the invention proposes that an air heatercorresponding to the existing parameters of the turbocharger be created.The components are connected in such a way that the hot air from the airheater flows into the turbocharger and the compressed air from thecompressor wheel into the air heater. The hot air flowing from theturbocharger can then be used for various applications. The air heaterconsists of a combustion chamber with a heat exchanger connectedupstream and known accessories.

In a further embodiment of the invention according to claim 2, a secondknown turbocharger without an impeller compressor as a working turbineis connected with the output of the first turbocharger and a shaft-powergas turbine is created in this way.

According to claim 3, the combustion chamber is dimensioned and adjustedto the turbocharger in such a way, and/or the turbocharger(s) (1, 2, 3)selected with respect to the flow cross section in such a way that adifferential pressure of 1.5 to 2.5 bar vis-à-vis the environment isproduced in the combustion chamber. In this way, the assembly operatesin the optimal range. According to claim 4, it is furthermore proposedthat the compressor of the turbocharger is connected with the gasgenerator or combustion chamber in a branched manner. Thus, one part(primary air) of the compressed air current is led into the combustionzone and the other part (secondary air) behind the combustion zone. Thesecondary air is mixed with the freshly combusted gases and cool them tosuch an extent that the allowable turbine temperature is not exceeded.Furthermore, the division of the air currents is designed in such a waythat it can be regulated, so that the afterburning and the exhaust-gastemperature is controllable.

Methods for producing various multistage assemblies of gas turbines areproposed in the further claims 5 to 7.

As a result of the new method, the use of a gas turbine instead of areciprocating engine is also possible for smaller outputs (30 to 200 kW)for the first time. To date, with smaller gas turbines, the specificprice per installed output was very high since the diversity of theirindividual components and their production costs was similarly high asthose of a gas turbine with a relatively high rated output. The costsare greatly reduced by means of the new method due to the use ofassembly groups (turbochargers) which are produced in large numbers andthus inexpensively and which were not originally designed for a gasturbine but are absolutely suitable. One can restrict oneself to theproduction of fewer connecting parts, lines of the working fluid, airheaters (combustion chamber, heat exchanger) and the assembly of smallgas turbines. This is completed by the fuel system, lubricating system,control and starting mechanism.

To produce a small gas turbine from the aforementioned individualcomponents, it is necessary on the one hand to adjust the air heater, inparticular the combustion chamber, accurately to the output parametersof the turbocharger, such as rotational speed and thus mass flow,combustion temperature, equipment temperature, inlet and outletvelocity, geometry of the connections to the combustion chamber and tothe turbine, inlet and outlet pressures, density of the gases andexhaust gas analysis. On the other hand, the assembly groups should beselected in such a way and adapted to the air heater that thecharacteristic curves of all assembly groups are adjusted to one anotherand that the required output and efficiency are attained.

In the present case, the complex shaped and high-grade turbine wheels,from a material point of view, and the also complex impeller compressorsare left to the specialist, while the producer of the small gas turbinecan restrict himself to the production of fewer connecting parts and theassembly of the small gas turbine.

A further advantage of this method lies in that a large number ofdifferent gas turbines can be produced as a result of combining variousor several similar turbochargers. In this way, many different small gasturbines (with respect to rated output, rotational speed, thermodynamiccircuit) can be produced with few assembly groups and with the aid of acomputer-supported element selection. A small gas turbine of this typecan be used independently of the arrangement and the number ofturbochargers involved, both as a shaft-power gas turbine and as a hotgas generator or air supplier. It can be used as a drive machine withgears or with electrical transmission or both in aircraft, watercraft,hovercrafts, motor vehicles and rail-borne vehicles, crawler-typevehicles and similar vehicles as well as agricultural machines, buildingmachines, emergency generators and power/heat coupling systems. Bothhigh-grade and inferior, conventional and alternative liquid and gaseousfuels can be used.

In claims 8 to 13, various assemblies for exhaust-gas driven turbines incombination with air heaters are proposed which can be used for manyapplications.

EXAMPLES

The method and the assembly shall be described in the following withreference to several examples.

FIGS. 1 to 12 show the individual variations of the assembly and flowdiagram.

A shaft-power turbine in a two-shaft design with a free-working turbineis shown in FIGS. 1 to 4 as example for the description in thethermodynamic circuit of gas turbine assemblies used most often. Thatis, from a thermodynamic point of view, this unit consists of a heatgenerator and a working turbine supported independently of the hot gasturbine.

The air is drawn in from the surroundings and compressed by thecompressor 5. The compressor 5 belongs to the first turbocharger 1. Thecompressed air flows into the heat exchanger 11 in which the air ispreheated by the exhaust-gas heat output. The compressed and preheatedair then enters the combustion chamber 12 where a portion of theatmospheric oxygen is used for the combustion of the fuel which reachesinto the combustion chamber 12 through the injection and air-injectionvalve 15. The combustion chamber 12 is designed in such a way that thehigh-tempered combustion product and the remaining air (secondary air)mix well and produce a technologically justifiable temperature of theworking fluid now designated as inlet gas. The inlet gas flows throughthe distributor into the compressor turbine 7 which is also a componentof the first turbocharger 1.

There, the gas delivers a large part of its energy to the compressorturbine wheel and therewith actuates the compressor 5. The gas thenflows through the connecting piece 13 into the working turbine 9, whichis a component of the second turbocharger 2. The mechanical power isthere transmitted to the working turbine shaft 10 and is availablethere. Furthermore, the gas is conveyed to the heat exchanger 11. A partof the remaining energy of the working gas in the form of heat is theregiven to the compressed air to raise the efficiency of the machine.Finally, the fluid which can now be described as exhaust gas flows viathe exhaust-gas diffuser 17 into the open. According to FIG. 2 a, theinlet gas may also first be conveyed into the working turbine 9 and theninto the compressor turbine 7 by an appropriate inversion of thearrangement.

The unit is actuated with the aid of the starter 18 which cansimultaneously be a generator. The spark plug 19 serves as the firstignition of the fuel/air mixture in the starting phase. A fuel pump 14or air-injection control is responsible for the fuel supply. The oilpump 16 conveys lubricant to the bearings. It is often not necessary fora drive unit that all shafts must be arranged in a coaxial or aligningmanner. The unit shown in FIGS. 1 to 4 demonstrates the compactness withthe selected arrangement. In this case, the shaft of the compressor andthe working turbine shaft are arranged at 90° to one another. Thisarrangement has no effect on the function of the machine; however, itleads to small deviations.

Very many different small gas turbines of various sizes can be realizedby combining turbochargers and connecting pieces of varying sizes. Thetype of gas turbine is determined by the intended application (providinghot gas, shaft power, radiated power or their combinations), the size bythe required output and the quality and technology of the availableturbocharger. All arrangements desired by a user and new combinationsare possible in this case.

In FIGS. 5 to 12, further possibilities of the assembly of a small gasturbine consisting of several turbochargers are shown. FIGS. 5 and 6show the assembly of FIGS. 1 to 4 with an additional axial step 8arranged on the compressor shaft in front of the compressor 5. Saidaxial step 8 increases the pressure ratio which exists aftercompression.

A small gas turbine of a two-shaft design with a compressor turbine anda free-working turbine is also shown in FIGS. 7 and 8. In this case, theworking turbine (10) lies parallel to the shaft of the compressor 5, incontrast to the arrangements in FIGS. 1 to 6. This arrangement isobtained by using another connecting piece 13 and changing theconnection on the heat exchanger 11.

FIGS. 9 to 12 show a multistage arrangement of a small gas turbine inwhich a heat exchanger can be omitted due to the larger pressure ratio.A further advantage of this arrangement is in the lower specific weight.In this case, the air is first precompressed in the low-pressurecompressor 4 and then brought to an overall higher pressure ratio thanin the single-step compression by the high-pressure compressor 5 andsupplied to the combustion chamber 12. The inlet gas then first of allflows through the high-pressure turbine 7 which drives the high-pressurecompressor 5, then through the working turbine 9 and finally through thelow-pressure turbine 6 which drives the low-pressure compressor 4.Finally, the exhaust gas flows through the exhaust-gas diffuser 17 intothe environment.

In this case also, another combination of the turbine assemblies ispossible, as shown in FIGS. 10 a and 10 b.

LIST OF REFERENCE NUMBERS

-   1 First turbocharger-   2 Second turbocharger-   3 Third turbocharger-   4 Low-pressure compressor-   5 Compressor/High-pressure compressor-   6 Low-pressure turbine-   7 Compressor turbine/High-pressure turbine-   8 Axial step-   9 Working turbine-   10 Working turbine shaft-   11 Heat exchanger Air heater-   12 Combustion chamber Air heater-   13 Connecting piece-   14 Fuel pump-   15 Air-injection valve-   16 Oil pump-   17 Exhaust-gas diffuser-   18 Starter-   19 Spark plug

1. Method for producing gas turbines in which prefabricated componentsor assembly groups are joined together to form gas turbines usingturbochargers of internal-combustion engines produced in series, whereinthe outlet of the compressor (5) of the turbocharger (1) is connectedwith the inlet of the gas generator or combustion chamber (12) and itsoutlet with the inlet of the exhaust-gas turbine, characterized in thatat least one further turbocharger (2, 3) is connected with the firstturbocharger (1) in such a way that the exhaust gas flows through theexhaust-gas turbines without branching, one of these turbochargers (2,3) is rebuilt as a working turbine (9) in which the compressor isreplaced by a coupling for a reduction in power, and the outlet of thelast turbocharger (2, 3) is connected with a heat exchanger (11) for thecombustion air.
 2. Method according to claim 1, characterized in that acombustion chamber (12) adjusted to the output parameters of ashaft-power gas turbine, is produced with heat exchanger (11) and fuelsystem, they are connected with a turbocharger (1) to form a hot gasgenerator, and the latter are joined together with a second turbocharger(2) without compressor as working turbine (9), selected according to theoutput parameters of the hot gas generator to form a shaft-power gasturbine.
 3. Method according to claim 1, characterized in that thecombustion chamber (12) is dimensioned and adjusted to the turbocharger(1, or 2, or 3), which drives the compressor, or the turbocharger(s) (1,2, 3) is/are selected with respect to the flow cross sections in such away that a pressure differential of 1.5 to 2.5 bar is produced vis-à-visthe environment in the combustion chamber (12).
 4. Method according toclaim 1, characterized in that the compressor (5) of the turbocharger(1) is connected with the gas generator or the combustion chamber (12),in front of and behind its combustion zone, so as to be branched andadjustable, so that the after-burning and the exhaust-gas temperature iscontrollable.
 5. Method according to claim 1, characterized in thatseveral turbochargers (1, 2, 3) of internal-combustion engines airheaters (11, 12) produced in parallel or multistage, in series, inaccordance with their output parameters, are joined with furtherassembly groups adapted to said turbochargers (1, 2, 3) to form ashaft-power gas turbine.
 6. Method according to claim 1, characterizedin that the outlet of the turbocharger (1) arranged first from aflow-line perspective, is connected directly or with a short connectingpiece (13) with the inlet of the second turbocharger (2) arranged afterit, so that the shafts of the turbocharger comprise an angle.
 7. Methodaccording to claim 1, characterized in that further assembly groups,such as heat exchanger (11), fuel system (14, 15), starter (18),control, etc. and parts for air heaters which are produced in series forvarious machines are connected directly or adapted to the turbochargersto form a gas turbine.
 8. Gas turbine assembly according to the methodaccording to claim 1, characterized in that the assembly groups such asturbochargers (1, 2, 3) of internal-combustion engines, heat exchangers(11), combustion chamber (12) and the like are connected directly or byway of short connecting pieces (13), predominantly at an angle, to forma compact unit.
 9. Gas turbine assembly according to claim 8,characterized in that the outlet of the turbocharger (1) of aninternal-combustion engine which acts as a hot gas generator isconnected via a connecting piece (13) with the inlet of the turbocharger(2) of an internal-combustion engine which acts as a working turbine.10. Gas turbine assembly according to claim 8, characterized in that theoutlet of the combustion chamber (12) is connected with the inlet of theturbocharger (2) which acts as working turbine and the outlet of theturbocharger (2) is connected via a connecting piece (13) with the inletof the turbocharger (1) which acts as compressor turbine.
 11. Gasturbine assembly according to claim 8, characterized in that theturbines (6, 7, 9) of 3 turbochargers (1, 2, 3) are connected in series,two acting as two-stage compressor turbines (6, 7) and one as a workingturbine (9), wherein the working turbine is arranged directly behind thecombustion chamber (12), from a flow-line perspective, in the central orlast position.
 12. Gas turbine assembly according to claim 8,characterized in that the shafts comprise an angle of about 90°.
 13. Gasturbine assembly according to claim 8, characterized in that the inletof the turbocharger (1) is connected with the combustion chamber 12 inan axially aligning manner and that the heat exchanger is arranged belowit parallel to the turbocharger 1.